110 MR. E. L. SHEELOCK ON THE EELATIONSHIP OF THE [Peb. I9II, 



IY. Conclusions. 



In considering the relation of the Permian and the Trias in the 

 North of England, the nature of the junction of the Permian Middle 

 Marl with the Bunter in South Nottinghamshire is of fundamental 

 importance. In a previous section stratigraphical evidence has been 

 adduced to prove that the junction is a strictly conformable one : 

 that the Permian Marl merges imperceptibly into the Bunter above; 

 and that, consequently, we must assume that the deposition of the 

 Bunter commenced immediately after the Permian Middle Marl had 

 been laid down. The evidence relied on is : 



(1) An apparent perfect upward passage from the Marl to the Bunter, 



visible in the Great Central Railway-cutting between Annesley and 

 Kirkby ; 



(2) A similar section in the Great Northern Railway near Kimberley ; 



(3) The fact that these cuttings are 6 miles apart shows that the 



apparent conformity extends over at least this distance, and is very 

 probably, therefore, a real conformity ; 



(4) Otber sections in brickpits, etc. showing similar relations, at intervals 



between Nottingham and Mansfield. 



To these arguments more general ones may be added. 



The thickness of the Middle Marl in South Nottinghamshire is 

 from 10 to 20 feet, so that if there was an unconformity between 

 it and the Bunter amounting to 1° only, the Marl would be entirely 

 overlapped in a distance of 300 yards (taking the thickness at a 

 maximum). It has, however, been followed continuously from 

 Nottingham to Mansfield (a distance of 12 miles), and in the whole 

 of that distance its apparent thickness varies by only a few feet. 

 Outlying spurs of high ground also enable us to trace it across the 

 strike, as from Watnall Chaworth to Bulwell (a distance of 3 

 miles), or from Skegby to Mansfield (a distance of 2 miles) ; and 

 here again the outcrop does not show any signs of being overlapped. 

 These facts can only be accounted for by a perfect conformity of 

 the Permian Marl with the Bunter. 



The folding map (PI. Y) shows that the Bunter and the Permian 

 have an identical strike ; whereas the Bunter and the Keuper, 

 between which there is evidence of a slight unconformity, have 

 slightly different strikes. 



Some possible objections have already been dealt with. The 

 absence of the Permian Marl at Mansfield, for about a mile in a 

 north and south direction, has been shown to occur in conjunction 

 with curious local characters in the limestone below ; and a theory 

 which explains both of these phenomena has been suggested, namely : 

 that limestone and marl are replaced at this point by the bar of a 

 Permian river, and that the Marl is really represented by sandrock 

 which has been mistaken for Bunter. At Warsop, where the Marl 

 again does not appear, the ground is overlain with alluvial deposits, 

 and this may prove to be the explanation of the apparent absence 

 of the Marl. On the other hand, the base of the Bunter is very 

 marly, and its lower portion may here represent the Marl. 



An explanation of the successive disappearance of the Permian 

 subdivisions from north to south, alternative to that of uncon- 

 formable overlap by the Bunter, is that each member of the 



